Improvement in lightning-rods for vessels



R. B. FORBES.

Lightning Rod.

No. 11,217. Patented July 4. I854.

1% a I Fig 2 UNITED STATES PATENT OFFICE,

ROBERT E. FORBES, OF BOSTON, MASSACHUSETTS.

IMPROVEMENT IN LIGHTNING-RODS FOR VESSELS.

Specification forming part of Letters Patent No. ll ,217, dated July 4,1854.

To all whom it may concern:

Be it known that I, ROBERT BENNETT Forums, of Boston, in the county ofSuffolk and State of Massachusetts, have invented a new and usefulImprovement in the Application of Li ghtnin g-Conductors to Ships orother Navigable Vessels; and I do hereby declare that the same is fullydescribed and represented in the following specification and theaccompanyin g drawings, letters, figures, and references thereof.

The great success of Sir William Snow Harriss method of constructin glightnin g-conductors and applying them to navigable vessels,particularly those of the British navy, has rendered it a matter ofgreat importance to de- Vise some means by which conductors involvingsimilar principles of action can be easily applied at any time to ships,and particularly those of the merchant service. The application of theHarris conductors to vessels must generally take place when the vesselis on the stocks or being constructed or is in dock or out of water.There is so much difficulty in mak ing the application when the vesselis in the water or is loaded with cargo as to prevent most ship ownersor masters from availing themselves of the benefits of the invention.

. Sir William Snow Harris, in the Edinburg New Philosphical J ournalremarks that the conductor hitherto employed at sea consists of longflexible chains or links of metal, and that, partly from inattention andpartly from prejudice, they frequently remain in the ships hold duringlong and hazardous voyages quite unemployed.

The necessity of providing the best possi ble security against theeffects of lightning on shipboard has been long admitted; but continuousand fixed metallic rods have been deemed inapplicable to ships,-inconsequence of their masts, the only parts to which they can beattached, being exposed to chances of injury, to motion in a variety ofways, to frequent elongation and contraction, and to the necessity whichfrequently arises for removing the higher masts altogether and placingthem on deck. It was probably from these causes that the small flexiblechains or links above mentioned were employed. Such conductors, owing totheir great want of continuity as well as their want of mass andsurface, are very unfavorable to the transmission of severe explosions,the electric matter becoming sensible at the points of junction, as isevident by the sparks upon them at the time of the discharge, so that insome instances they have become actually disunited. They are likewiseobjectionable as being liable to every species of injury incident to aships rigging, and much difficulty is experienced in keeping them intheir position and unbroken, more especially during gales of wind and atnight, and when it is, perhaps, required (as has already been observed)to remove some portions of the higher masts. It has therefore been longconsidered desirable to apply, if possible, a permanent conductor,

which should always be in its place and ready for action.

To protect a ship effectually from damage from lightning it is essentialthat a conductor be as continuous and direct as possible from thehighest point to the sea, that it be permanently fixed on the maststhroughout their whole extent, so as to admit of the motion of oneportion of the mast upon another, and in case of removal of any part ofthe mast together with the conductor attached to it, either fromaccident or design, the remaining portion should still be perfect andequivalent to transmit an electrical discharge into the sea. To fulfillthese conditions pieces of sheet-copper from one-eighth to one-sixteenthof an inch thick and about two feet long, and varying from sixinches toone inch and ahalf in breadth, may be inserted into the masts in twolaminae, one over the other, the butts or joints of the one beingcovered by the central portions of the other. The laminze should beriveted together at the butts, so as to form a long elastic continuousline. The whole conductor is inserted under the edges of a neat grooveplowed longitudinally in the aft side of the different masts and securedin its position by wrought-copper nails, so as to present a fairsurface. The metallic line thus constructed will then pass downward fromthe copper spindle at the mast-head along the aft side of the royal-mastand the topgallant mast, being connected in its course with the copperabout the sheave-holes. A copper lining the aft side of the capthrouglnwhich the top-mast slides, now

takes up the connection and continues it over the cap to the aft side ofthe top-mast, and so on as before to the step .of the mast. Here itmeets athick,wide copper lining twined around the step under the heel ofthe mast, and resting on a similar layer of copper fixed to the keelson.This last is connected with some of the keelson-bolts and with threeperpendicu lar bolts of copper of two inches in diameter, which aredriven into the main keel upon three transverse or horizontal boltsbrought into immediate contact with the copper expanded over the bottom.The laminae of copper are turned over the respective mast-heads andsecured about an inch or more down on the opposite side. The cap whichcorresponds isprepared in a similar way, the copper being continued fromthe lining on the aft part of the round hole over the cap into the forepart of the square one, where it is turned down and secured as before,so that when the cap is in place the contact is complete. In this way wehave a continuous metallic line from the highest points to the sea,which will transmit the electric matter directly through the keel, beingthe line of least resistance.

I have been thus particular to state theprincipleofHarrissinvention,andinhisown words, in order that myinvention may be more readily comprehended. It will therefore be seenthat, as a general thing, it would be very difficult,

ifnot absolutely impossible, to apply Harriss conductor entire to amerchant vessel when afloat or loaded with cargo. Besides this, it is avery expensive conductor. While my invention secures the principaladvantages of that of Harriss, as described, it is particularlyapplicable to a vessel either laden, unladen, or afloat, as well as whenin port or at sea, and has all the advantages of permanency that can bedesired. It will answer for vessels of war as well as those of themerchant service.

I make use of the Harris plan of conductor from the top of the mast downto, or nearly to,

the eyes of the lower rigging, terminating the same at some convenientpoint on the head of the lower mast. From thence 1 branch ed to the twoafter-shrouds, or to any other shrouds, by means of a system ofsocket-tubes and tubes or rods, or their equivalents, extended down theshrouds and over and against the outside of the hull to the coppersheathing, or down to such a depth on the hull that the lower end of theconductor shall always remain immersed in the water under the ordinaryrollingorpitching of the vessel when at sea.

I would remark that the principle of extending a conductor down theshrouds is not new with me, as this also was suggested by Sir WilliamSnow Harris several years ago. My invention has relation moreparticularly to an improved mode of constructing or applying such aconductor.

Of the drawings above mentioned, Figure 1- tion as applied thereto. Fig.2 is a side view of the same. Fig. 3 is a longitudinal section of themast. Fig. 4 is a side view, and Fig.5 is a section on an enlargedscale, of the mode of making that part of the conductor which is appliedto the shrouds. They also exhibit the mode of connecting it with theshrouds.

A, Figs. 1 and 3, represents the course of the conductor from the top ofthe mast down to where it branches off from thelower'm ast-head, k, suchconductor being constructed of plates or thin bars of metal whose endsare lapped over one another and secured together and to the mast bycopper nails. This construction of such part of the conductor and itsapplicatlon to the mast does not differ materially from that of Harriss,hereinbefore mentioned. Each movable portion of the mast is to have aseparate portion of the conductor aflixed to it, as in the plan ofHarris, so that it may be moved as circumstances may require and notdestroy the electric connection.

The branches down one or both the shrouds on opposite sides of the mastare to be constructed'as follows, they being shown at B B: Each consistsof a series of metallic sockettubes, to a a, &c., made to receive othertubes, 1) b b, &c., of greater length. Generally speaking, eachsocket-tube should be made of an internal diameter sufficiently large toreceive the two ends of two of the tubes b b b, and the socket-tubeshould be lashed at its middle to the shroud, and to have pins 0 c orprojections or suitable contrivances extending from it just above andbelow the lashing d, in order to hold it in place. It should belongenough to allow of the shrinkage and expansion or usual taking up orletting out of the shroud. For this purpose it may be about fifteeninchesin length. The slide-tubes b b may be much longer, and each may beseized or lashed to the shroud at such number of points between thesocket-tubes in which it is inserted as circumstances may re quire. Thissystem of connected tubes may be extended over the side of the vesseland through the channels, and thence to, and be attached to, the coppersheathing g, or to a metallic bar or plate extended down so far towardthe keel as to have its lower end always immersed in water under anyrolling or pitching motion of the vessel While at sea.

Thus a complete system of tubing, flexible in its nature, presenting agreat amount of electric surface both internally and externally, and atthe same time sufficiently permanent to be independent of any daily careof the crew, will be secured at a reasonable expense. One great featureof this system is that any ship built and loaded, with lower masts in,can be fitted with the conductors as well as if originally designed tohave them.

The plates on the masts should be placedin grooves sufficiently deep toadmit the sections so that they will not in any way interrupt the easypassage of the parrals. Said plates may be secured or fixed either bynails or screws,

and they ought to be of asize and surface sufficient to properly convey0E any discharge of electricity or stroke of lightning. They may be madeof any suitable conducting metal or material or composition of metals ormaterials.

I disclaim any idea of attempting to improve on the Harris conductor asfitted to pass through the hold of a vessel, but affirm that my plan ofconstructing a conductor applied to the mast and shroud and led over theside of the vessel (instead of down through the hold) and attached tothe copper or extended down toward the keel, as stated, has advantageswhich are not possessed by said Harriss' plan, which cannot be attachedto the shrouds, my plan being particularly applicable in the merchantservice, where I believe it will be the means of saving manylives andmuch property.

I do not claim the system of permanent conductors as applied to the mastof a vessel in the manner well known as that of Sir William Snow Harris,wherein the conductor is carried down the mast and through the hold andkeel of the vessel; nor do I claim either the common chain or rodconductor, nor the mode or modes of applying the same; nor do I claim tomake the conductor of fixed lines of metal and to extend down the mastto near the lower mast-head, and from thence down the after-swifters tothe ships side; nor do I claim to make that part of the condiictorextending down on the after-swifter or shroud as one long tube or metal;but

What I do claim is--- Composing it of a system of socket-tubes andslide-tubes, and confining the same to one of the shrouds or the riggingand over and against the outside of the hull, and either to the coppersheathing thereon or down to such a depth on the hull that the lower endof the conductor shall always remain immersed in the water under theordinary rolling or pitching of the vessel while at sea, allsubstantially as specified.

In testimony whereof I have hereto set my signature this 23d day ofJuly, A. D. 1853.

R. B. FORBES.

Witnesses:

R. H. EDDY, T. P. HALE, Jr.

